1. Field of the Invention:
The present invention relates to sheet metal tools of the type used for cutting and abrading operations and, specifically, to a method for chemically machining such tools to provide cutting teeth of unique and highly efficient shapes.
2. Description of the Prior Art:
Thin cutters and files, by their very design, have traditionally been very dull. They tend to load with the material being cut and clog. This necessitates cleaning before more material can be removed from the work surface. Because of this loading condition, most users rub material off the work surface by friction instead of actually removing material by creating a chip. It was very difficult to create a sharp cutting edge on prior art cutters and files because of the manufacturing techniques utilized. The problem was increased if the cutter or file in question had a multiplicity of cutting edges. The prior art also required that most cutters or files be stiff or rigid, which generally prohibited the cutter or file from conforming to a curved shape. Although abrasive papers were introduced in an attempt to solve this problem, the paper or cloth abrasive media tended to rub off material and create heat rather than cut material from the work surface.
Many of the cutters or files that are manufactured at the present time are punched out of a suitable sheet metal material. The material is passed through a punch and die, thereby imparting holes in the metal that are bent to provide the "set" which is necessary to make the desired tooth profile. The state-of-the-art cutters and files lack a preferred degree of sharpness. This is partially the result of the cutting edges being formed by the ragged die cuts in the metal blank. More expensive cutters and files have ground edges, however this grinding process is limited in application and limited in possible tooth arrangements because the grinding wheel or broach is required to enter and exit the tooth in a straight line. As a result, the available tooth patterns are relatively simple and linear.
Because of the high cost of tooling and grinding, attempts have been made in the prior art to manufacture sheet metal files by means of chemical etching processes. These endeavors have not generally met with commercial success because the end product tended to do more rubbing than cutting. This is primarily due to lack of side, frontal and/or top relief in the etched individual tooth patterns. U.S. Pat. No. 3,045,321 to McDermott is an example of such an abrading device. Etching through duplicate patterns of resists applied to opposite sides of a metal blank so that the etched cavities penetrate completely through the blank from opposite sides works very poorly in practice. As will be explained, the resulting reliefs or clearances extend in the wrong direction, causing the tool to rub more than it will cut.
U.S. Pat. No. 4,240,806 to Francen, is an improvement over the McDermott manufacturing method and makes use of special resist patterns on the metal blank. However, this patent also lacks sufficient top relief or clearance due to the geometry created by the chemical breakdown of metal as it is removed from the metal blank during the etching process. As a result, the tool tends to rub the work surface rather than cut and has the undesirable characteristic loading or clogging previously discussed.
It is an object of the present invention to provide an improved chemical machining method for manufacturing cutting tools which overcomes the previously mentioned shortcomings.
Another object of the invention is to provide a greater array of tooth designs for such tools that more efficiently cut a work material than the presently available designs.
Another object of the invention is to provide a linear file blade which can be mounted in a tensioned state within a frame to be used as an improved rasp or as a hacksaw.
Another object of the invention is to provide an improved linear or circular file which can be used with a backing plate for the purpose of providing required stiffness or rigidity.
Another object of the invention is to provide an improved flexible etched file that can be used to work irregularly shaped work surfaces.
Another object of the invention is to provide an improved sheet metal file and method of manufacture that eliminates the necessity of grinding the cutting edges or the use of expensive dies and fixtures.
Another object of the invention is to provide a manufacturing method which provides the top and side tooth relief angles necessary to efficiently remove material from a work surface.